Method and apparatus for incorporating fibrous materials into air-free high solids dispersions



J. J. GRABAUSKAS El'AL METHOD AND APPARATUS FOR INCORPORATING FIBROUS MATERIALS May 5, 1970 3,510,109

INTO AIR-FREE HIGH SOLIDS DISPERSIONS Filed Feb. 8, 1968 United States Patent 3,510,109 METHOD AND APPARATUS FOR INCORPORAT- ING FIBROlUS MATERIALS INTO AIR-FREE HIGH SOLIDS DISPERSIONS I Joseph J. Grabauskas, Chicago, and William F. Underwood, Oak Park, Ill., assignors to Union Carbide Corporation, a corporation of New York Filed Feb. 8, 1968, Ser. No. 704,097 Int. Cl. B01f 7/02 US. Cl. 259-18 8 Claims ABSTRACT OF THE DISCLOSURE Fibrous materials are incorporated into air-free dispersions having a high solids content. The fibrous-containing air-free dispersions are subsequently fabricated to obtain formed structures which are substantially free of air bubbles.

This invention relates to a method and apparatus for incorporating fibrous materials into air-free dispersions having a high solids content.

The incorporation of fibrous materials, such as cellulose, hemp high molecular weight organic fiocculants, collagen, regenerated cellulose and the like, into dispersions having a high solids content is desirable since these fibrous materials assist in controlling the hydrothermal shrink characteristics and dimensional stability as well as impart added strength to the products produced from these dispersions. Typical of the products that can be fabricated from dispersions having a high solids content are such items as sheets, tubing, fibers, food casings, and the like.

Prior attempts to incorporate fibrous materials into airfree high solids-containing dispersions have not been successful because of the difliculties encountered in uniformly dispersing the fibers into these dispersons and maintaining them in an air-free state. The commercial methods presently utilized to accomplish this typically include sifting the fibers into the high solids-containing dispersions and then attempting to uniformly blend the fibers in the dispersion by mechanical means followed by removing the air by evacuation. Generally, these methods have not met with success due to the tendency of the fibers to agglomerate and form small, ball-like formations, during sifting. Usually, these small, ball-like formations remain intact when placed in the dispersion despite the use of mechanical mixing means to incorporate them in the dispersion.

=It is an object of this invention, therefore, to provide a method and apparatus for uniformly incorporating fibrous materials into air-free dispersions having a high solids content while maintaining the dispersions in an air-free state.

This and further objects of the invention will become more clear from the ensuing discussion.

It has now been found that the objects of the invention can be generally attained by providing an apparatus and method for separating the individual fibers of a fibrous material by subjecting the fibers to a sudden transition from atmospheric pressure to a reduced pressure zone; and, blending the thusly separated fibers into an air-free high solids-containing dispersion which is maintained under a reduced pressure.

The fibrous materials which can be utilized in this invention are those readily obtained from such natural and synthetic materials as cellulose, cotton, rayon and the like and such other natural or synthetic materials such as alginates, starches and the like. Hence, use of the terms fibrous material or fibrous materials throughout this 3,510,109 Patented May 5, 1970 application and in the appended claims should be understood as and is intended to refer to and include the fibrous materials listed above as well as their equivalents.

The invention will become more clear when considered together With the accompanying drawing which forms a part thereof and which is set forth as being merely illustrative and exemplary of the apparatus which can be employed in the invention and wherein:

FIG. 1 is a schematic elevational view, part in section-and broken away, of one embodiment of the apparatus of the invention; and,

FIG. 2 is an exaggerated perspective view of a portion of the apparatus of FIG. 1.

Turning now to the drawing wherein like reference numerals denote like parts there is shown in FIG. 1 a container 10 which can serve as a supply or reservoir for fibrous materials 14. In lieu of the container 10 other means, such as a conveyor belt, trough, and the like, can be utilized with equal facility to supply and retain the fibrous materials 14 of the invention.

Reference numeral 16 generally designates a conventional vacuum mixer vessel equipped with a mechanical mixing blade 17 into which a high solids-containing dispersion 18 is placed. The vacuum mixer vessel 16 is provided with a cover 20 having a conduit 22 which communicates at one end with the interior of the vacuum mixer vessel 16 and whose other end is positioned adjacent container 10.

As shown in more detail in FIG. 2, the end of conduit 22 positioned adjacent container 10 has a slot formed therein which slot is denoted by reference numeral 24. Although the size and shape of the slot 24 is not critical, it should be of such configuration and size as to readily permit the flow of individual fibers therethrough without permitting such a quantity of fibers to flow therethrough so that therethrough so that there results fiber agglomeration or interference with the subsequent distribution of the fibers in the high solids-containing dispersion. Preferably, slot 24 is rectangular in shape and measures about of an inch in width and about A of an inch in length. The other end of conduit 22, communicating with the interior of the vacuum mixer vessel 16, is provided with an inverted funnel 26 extending into the vacuum mixer vessel 16 to further facilitate the distribution of the fibrous materials 14 in the high solids-containing dispersion 18.

Reference numeral 28 generally denotes a conventional vacuum pump equipped with air traps 30 and communicating with the interior of the vacuum mixer 16 through conduit 32 at port 34.

A typical operation of the readily comprehended when considered together with the accompanying drawing.

A dispersion 18 having a high solids content is first placed in the vacuum mixer vessel 16 and fibrous materials 14 are placed in and supplied to container 10 either manually or by mechanical feed means, such as a hopper (not shown), to maintain a depth of from about A; to about A of an inch of fibrous material 14 in the container 10. The vacuum mixer vessel 16 is now started and cover 20 is placed in position thereon. After cover 20 is secured to the vacuum mixer vessel 16, the vacuum pump 28 is started and set to draw a vacuum of from about 5 to 7 inches of mercury (Hg) in the vacuum mixer vessel 16, thereby removing the air from and creating a partial vacuum in the vacuum mixer vessel 16 to obtain an air-free dispersion 18. The container 10 is then brought into proximity to slot 24 at the inlet end of conduit 22 so that the individual fibers of the fibrous material 14 can be drawn into conduit 22, and transmitted therethrough into the vacuum mixer vessel 16.

This effect is achieved due to the pressure differential created in the vacuum mixed 16 which pressure differential also acts upon the end of conduit 22 communicating with the interior of the vacuum mixed 16 and which is thereby translated throughout the length of conduit 22. Since the cross-sectional area of conduit 22, as Well as that of orifice 24, is many times smaller than the unoccupied, cross-sectional area of vacuum mixer 16 above the high solids-containing dispersion 18, a high velocity air flow is created through conduit 22 as a result of a given air volume being displaced through the smaller cross-sectional area of conduit 22 in a given time interval. Consequently, the fibrous material 14 is also conveyed through conduit 22 at a high velocity. However, upon leaving conduit 22 and entering the larger cross-sectional area in the vacuum mixer 16, the air and the fibrous material 14 being conveyed at high velocities through conduit 22 suddenly lose their high velocities, whereupon the fibrous material 14 floats down onto and is deposited in the air-free, high solids-containing dispersion 18 by the force of gravity acting upon. it. The inverted funnel 26 serves to deflect the now low velocity fibrous material 14 toward the high solids-containing dispersion 18 and also prevents the fibrous material from entering conduit 32. In order to further assist in preventing fibrous materials 14 from entering conduit 32, port 34 can be located adjacent to the point where inverted funnel 26 is secured to the vacuum mixer vessel 16. Additionally, the cross-sectional area of conduit 32 should preferably be from about 3 to 4 times larger than that of conduit 22 so that the air being continuously evacuated from the vacuum mixer vessel 16 is conveyed through conduit 32 at a low velocity so that it does not interfere with the deposition of the fibrous material 14 in the high solids-containing dispersion 18.

In order to assure that all the fibers of the fibrous material 14 are removed from container 10, the container can be actuated to traverse from side to side beneath slot 24, either manually or by conventional mechanical means, until that quantity of fibrous material 14 desired or required to be incorporated in the air-free, high solids dispersion 18 has been removed therefrom. Obviously,

container 10 can be repeatedly filled with fibrous material 14 as often as and to the extent that is necessary depending upon the amount of fibrous material 14 desired or required to be incorporated in the high solids-containing dispersion 18. As soon as the desired or required quantity of fibrous material 14 has been transferred to the vacuum mixer vessel 16, a full vacuum of 28 inches Hg is drawn on the vacuum mixer vessel 16 and the orifice 24 at the inlet end of conduit 22 is closed, such as by capping this end of conduit 22, so that all the air can be evacuated from the vacuum mixer vessel 16. Mixing of the fibrous material 14 in the air-free high solids dispersion 18 is then continued until a uniform blend of the individual fibers is attained in the air-free, high solidscontaining dispersion 18.

It has been found that maintaining a full vacuum of 28 inches Hg on the vacuum mixer vessel 16 for a period of from about 10 to 20 minutes is sufficient to attain an air-free, high solids-containing dispersion. As a result, it has been found that these air-free high solids dispersions can be subsequently fabricated such as by extrusion, calendering, molding and the like, to obtain such items as films, tubes, casings and the like, which are substantially free of weak pores normally caused by the presence of air bubbles.

It has also been found that an initial absolute pressure differential of between about 2.0 to 3.5 p.s.i. at the beginning of the mixing of the high solids-containing dispersion 18 and the fibrous material 14 will act to substantially reduce or eliminate the distribution of large air pockets into many small air bubbles throughout the high solids-containing dispersion 18. This, in turn, gives rise to a relatively short deaeration cycle of from about 10 to 20 minutes when a vacuum of 28 inches Hg is applied to the vacuum mixer vessel 16.

The following example is set forth as being further illustrative and exemplary of the apparatus and method of the invention and is not intended, in any way, to be limitative thereof. In the example all parts and percentages are by weight unless otherwise indicated.

EXAMPLE A collagen dispersion containing about 10 percent solids was prepared in the usual manner from 3,082 grams of untreated beef tendon by subjecting the beef tendon together with crushed ice to a series of size-reducing operations wherein the ice-beef tendon mixture was progressively ground, minced, fibrillated and the like until a collagen dispersion was obtained all according to procedures well known to those skilled in the art. Prior to placing this collagen dispersion into a vacuum mixer vessel, the vacuum mixer was precooled to about 0 C. The collagen dispersion was then placed in the vacuum mixer vessel, the cover was secured thereto and a vacuum of from about 5 to 7 inches Hg was drawn thereon. The collagen dispersion was then mixed until it attained a temperature of about 3 C. Cotton fibers were placed in a container to a depth of from about A; to A of an inch. The cotton fibers were then transferred to the vacuum mixer vessel in an amount sufiicient to result in a dispersion having a total solids content of about 8.6 percent. In this instance, about 39 grams of cotton fibers were used which were calculated to be about 22 percent of the collagen content of the dispersion. After the required quantity of cotton fibers had been transferred to the vacuum mixer vessel, a full vacuum of 28 inches Hg was drawn on the vacuum mixer vessel and the conduit transferring the cotton fibers to the vacuum mixer was closed off. Mixing of the collagen dispersion containing the cotton fibers was then continued for a period of about 20 minutes under the full vacuum of 28 inches Hg. At the end of this time, the dispersion was examined and found to be free of any small, ball-like formations or agglomerations of the cotton fibers.

Although the invention has been described in some detail and with particularity it should be understood that changes, modifications and alterations can be made therein without departing from the scope and spirit of the invention.

What is claimed is:

1. A method for uniformly incorporating fibrous materials into an air-free dispersion having a high solids content including the steps of:

(a) mixing a dispersion having a high solids content;

(b) subjecting the mixed dispersion to a partial vacuum;

(0) creating an air flow between the mixed dispersion and a source of supply of fibrous material;

(d) conveying by means of the air flow created, the fibers of the fibrous material to and depositing them in the dispersion during the mixing thereof;

(e) stopping the air fiow created such that the fibers of the fibrous material are no longer conveyed to and deposited in the dispersion;

(f) increasing the vacuum drawn on the dispersion containing the separated fibers mixed therein; and,

(g) continuing the mixing of the fibers in the dispersion until a uniform, substantially air-free blend of the dispersion containing the fibers is obtained.

2. The method of claim 1 wherein the mixed dispersion is first cooled to a temperature of from about 0 C. to 5 C.

3. The method of claim 1 wherein the mixed dispersion is subjected to a partial vacuum of from about 5 to 7 inches Hg.

4. The method of claim 1 wherein the vacuum applied to the dispersion having the fibers mixed therein is about 28 inches Hg.

5. The method of claim 4 wherein the mixing of the fibers in the dispersion is continued for a period of from about 10 to 20 minutes.

6. A method for uniformly incorporating a fibrous material into an air-free dispersion having a high solids content including the steps of;

(a) mixing a dispersion having a high solids content;

(b) subjecting the mixed dispersion to a partial vacuum of from about 5 to 7 inches Hg such that an air flow is created between the dispersion and a source of supply of fibrous material;

(c) conveying the fibers of the fibrous material by means of the air flow created to and depositing them in the dispersion during the mixing thereof;

(d) stopping the air flow created such that the fibers of the fibrous material are no longer conveyed to and deposited in the dispersion;

(e) increasing the vacuum of the dispersion having the fibers mixed therein to about 28 inches Hg; and,

(f) continuing the mixing of the fibers in the dispersion under the increased vacuum for a period of from about 10 to 20 minutes such that there is obtained therefrom a uniform, substantially air-free blend of the dispersion containing the fibers.

7. The method of claim 6 wherein the mixed dispersion is first cooled to a temperature of from about C. to C.

8. An apparatus for uniformly incorporating a fibrous material into an air-free dispersion having a high solids content comprising, in combination;

(a) a vacuum mixer vessel into which a dispersion having a high solids content is placed;

(b) means for evacuating air from said vessel, including a first conduit, one end of which communicates with the interior of said vessel;

(0) a supply source for supplying fibrous material;

((1) a second conduit through which such fibrous material is conveyed, one end of said second conduit communicating with the interior of said vessel and the other end communicating with said supply source; the cross sectional area of said second conduit being smaller than the cross-sectional area of said first conduit to promote a high velocity air flow through said second conduit and (e) means in said vessel associated with said second conduit to facilitate distribution of said fibrous material in said dispersion;

(f) the end of said second conduit communicating with said supply source having an orifice smaller than the diameter of said conduit to facilitate flow of individual fibers therethrough and inhibit agglomeration of fibers therein;

(g) the larger cross sectional area of said first conduit relative to that of said second conduit promoting low velocity air flow through said first conduit, thus inhibiting flow of fibrous material out of said vessel.

References Cited UNITED STATES PATENTS 3,134,576 5/1964 Lopige 25,9-21 3,175,807 3/1965 Gouveia 259-21 FOREIGN PATENTS 1,007,509 10/ 1965 Great Britain.

ROBERT W. JENKINS, Primary Examiner 

